In an engagement device provided with a hydraulic actuator having an oil bag expanding and contracting in an engaging direction and a releasing direction, an annular engagement plate moved by the oil bag in the engaging direction and the releasing direction, and a return mechanism that urges the engagement plate in the releasing direction, the engagement plate is an engagement element whose surface on the releasing direction side is in contact with the oil bag, and the return mechanism moves the engagement plate in the releasing direction and presses the oil bag through the engagement plate.

An automatic transmission includes a clutch device having a clutch hub, a clutch drum, a friction plate, a piston, and a hydraulic chamber. The clutch drum includes an outer-side cylindrical portion, a disc-shaped first radial portion extending radially inwardly, an axial portion extending axially from the first radial portion, and a disc-shaped second radial portion extending radially inwardly from the axial portion. The piston includes a pressing portion disposed between the first radial portion and the friction plate side, and a disc-shaped piston radial portion extending radially inwardly from the pressing portion. The hydraulic chamber is provided radially inwardly from the axial portion and on the non-friction-plate side of the piston radial portion. A comb-teeth portion is provided at a radially intermediate portion of the piston radial portion. The axial portion and the piston radial portion intersect with each other in a comb-teeth shape.

An automatic transmission includes a clutch device having a clutch hub, a clutch drum, a friction plate, a piston, and a hydraulic chamber. The clutch drum includes an outer-side cylindrical portion, a disc-shaped first radial portion extending radially inwardly, an axial portion extending axially from the first radial portion, and a disc-shaped second radial portion extending radially inwardly from the axial portion. The piston includes a pressing portion disposed between the first radial portion and the friction plate side, and a disc-shaped piston radial portion extending radially inwardly from the pressing portion. The hydraulic chamber is provided radially inwardly from the axial portion and on the non-friction-plate side of the piston radial portion. A comb-teeth portion is provided at a radially intermediate portion of the piston radial portion. The axial portion and the piston radial portion intersect with each other in a comb-teeth shape.

A clutched joint module comprising an output member and an input member rotatable relative to each other about an axis of rotation; a primary actuator operable to apply a primary torque to rotate the output member about the axis of rotation; and a clutch mechanism operable between an engaged state and a disengaged state to facilitate application of the primary torque. The clutch mechanism can comprise a plurality of plates and an actuator operable to compress the plurality of plates to cause the clutch mechanism to function in the engaged state. The actuator can be a ball-ramp clutch device. A quasi-passive elastic actuator can be coupled to the input member and can be operable, via the clutch mechanism, to release stored energy to apply an augmented torque to assist rotation of the output member. Associated methods and systems are disclosed.

A clutched joint module comprising an output member and an input member rotatable relative to each other about an axis of rotation; a primary actuator operable to apply a primary torque to rotate the output member about the axis of rotation; and a clutch mechanism operable between an engaged state and a disengaged state to facilitate application of the primary torque. The clutch mechanism can comprise a plurality of plates and an actuator operable to compress the plurality of plates to cause the clutch mechanism to function in the engaged state. The actuator can be a ball-ramp clutch device. A quasi-passive elastic actuator can be coupled to the input member and can be operable, via the clutch mechanism, to release stored energy to apply an augmented torque to assist rotation of the output member. Associated methods and systems are disclosed.

A power transmission device includes a selective rotation transmission mechanism for keeping the current drive mode of a vehicle. The selective rotation transmission mechanism includes a magnetized yoke, and a pressure receiving plate opposed to the yoke in the axial direction. In order to improve the stability of operation of the selective rotation transmission mechanism, the yoke and the pressure receiving plate are configured such that separated regions are defined between the yoke and the pressure receiving plate when the latter is attracted to the former such that at the separated regions, the yoke is not in contact with the pressure receiving plate.

A power transmission device includes a selective rotation transmission mechanism for keeping the current drive mode of a vehicle. The selective rotation transmission mechanism includes a magnetized yoke, and a pressure receiving plate opposed to the yoke in the axial direction. In order to improve the stability of operation of the selective rotation transmission mechanism, the yoke and the pressure receiving plate are configured such that separated regions are defined between the yoke and the pressure receiving plate when the latter is attracted to the former such that at the separated regions, the yoke is not in contact with the pressure receiving plate.

A vehicle drivetrain assembly having a clutch collar actuator mechanism. The clutch collar actuator mechanism may include an air bellow and a fork that may operatively connect an actuator rod to a clutch collar. The clutch collar actuator mechanism may actuate the clutch collar from a first position to a second position when the air bellow is inflated.

A hydrostatically operated clutch system having a hydrostatic clutch actuator for hydrostatically operating a clutch, in particular a pulse separation clutch of a hybrid drive, such that the hydrostatic clutch actuator is combined with a valve arrangement which is to be opened actively and enables the clutch to be engaged rapidly.

A clutched joint module comprising an output member and an input member rotatable relative to each other about an axis of rotation; a primary actuator operable to apply a primary torque to rotate the output member about the axis of rotation; and a clutch mechanism operable between an engaged state and a disengaged state to facilitate application of the primary torque. The clutch mechanism can comprise a plurality of plates and an actuator operable to compress the plurality of plates to cause the clutch mechanism to function in the engaged state. The actuator can be a ball-ramp clutch device. A quasi-passive elastic actuator can be coupled to the input member and can be operable, via the clutch mechanism, to release stored energy to apply an augmented torque to assist rotation of the output member. Associated methods and systems are disclosed.